A solution of 15-methyl-PGF2α (185 mg.) in 2.5 ml. of an anhydrous, oxygen-free xylene containing 2,2'-dipyridyl disulfide (165 mg.) and triphenylphosphine (196 mg.) is stirred under nitrogen for 2.5 hr. at 25° C. The mixture is diluted with 150 ml. of xylene and heated at reflux for 3 hr. TLC (80 percent EtOAc/hexane) shows essentially a single, less polar product. The xylene is removed by evaporation at reduced pressure to afford a residue which is diluted with ice/water/sodium bicarbonate and ethyl acetate and extracted thoroughly with ethyl acetate. The ethyl acetate extract is washed with brine, dired over anhydrous sodium sulfate and concentrated to afford a residue of (15S)-15-methyl PGF2α, 1,9-lactone. The residue is purified by chromatography on 50 g. of neutral silica packed with 10 percent acetone/methylene chloride and eluted (5 ml. fractions) with 200 ml. of 10percent acetone/methylene chloride, 1500 ml. of 20 percent acetone/methylene chloride and 1000 ml. of 35 percent acetone/methylene chloride.
